Recently, communication apparatuses such as mobile phones are remarkably spread, and the communication apparatuses mounted with various functions are used in various regions.
Note that the recent communication apparatus is smaller and lighter, and its operability is good, thereby being extremely convenient. One can communicate with the communication apparatus without any inhibition at any place within a communication range.
However, with the increase in number of communication apparatus, a trouble such that the communication apparatus is passed on to anyone other than the owner increases due to the communication apparatus being misplaced, stolen and the like. Also, a situation occurs where anyone other than the owner uses the communication apparatus without permission.
Given this situation, as one of documents filed prior to the present invention, there is a document disclosing a technology which can make a device itself such as a mobile phone unavailable and warn that the device is away beyond a certain distance, when the device is away from the owner or user due to the device being misplaced or stolen (for example, see Patent Document 1).
In the above-mentioned Patent Document 1, an identification signal transmitting unit and a usage restriction canceling unit are attached to the target device. When a distance between the above-mentioned units is below a certain distance, the usage restriction canceling unit transmits a usage restriction canceling signal to the target device. When the distance between the above-mentioned units becomes beyond the certain distance, and a reception level of a code signal received in each unit from the opposite unit becomes less than or equal to a predetermined value, the above-mentioned usage restriction canceling unit stops the transmission of the usage restriction canceling signal. Then, the identification signal transmitting unit sends out a warning signal. Therefore, it is possible to make the target device itself unavailable and to warn that the target device is away beyond the certain distance, when the target device is away from the owner or user.
Further, there is a document disclosing a technology which facilitates dial lock and unlock in a mobile phone, and prevents others from using the mobile phone when it is lost with unlocked (for example, see Patent Document 2).
In the above-mentioned Patent Document 2, an unlock code transmitting unit built into an unlock device transmits a radio wave on which an unlock code is superimposed. An unlock code receiving unit in the mobile phone receives this unlock code to be compared with a code preliminarily recorded in a control unit. When the codes are coincident, the unlock code receiving unit unlocks the dial lock. In this condition, when the code is not received for a certain period of time (when the unlock device is away), the unlock code receiving unit relocks the dial lock. Therefore, it is possible to facilitate the dial lock and unlock in the mobile phone, and to prevent others from using the mobile phone when it is lost with unlocked.
Further, there is a document disclosing a portable information device which makes it unnecessary to prepare and carry a particular device for the prevention of the loss (for example, see Patent Document 3).
In the above-mentioned Patent Document 3, the portable information device, into which a near field communication function between devices is built, uses its function to recognize a communication error which occurs when any one of the devices is away from another one of the devices beyond a certain distance, and broadcasts the recognition. Therefore, it is unnecessary to prepare and carry the particular device for the prevention of the loss.
Further, there is a document disclosing a technology which can prevent others from using a mobile terminal without permission, and improve the security (for example, see Patent Document 4).
In the above-mentioned Patent Document 4, a restriction condition such as times and places where the mobile terminal can be used is added to authentication information transmitted from an authentication card of the user to the mobile terminal. Therefore, it is possible to perform detailed authentication depending on the situation, prevent others from using the mobile terminal without loosing the convenience, and improve the security.
Furthermore, there is a document disclosing a technology which can not only provide more flexibility on the authenticating side but also respond to a broadband service by using one physical terminal (user terminal) held by a user, and authenticate various services (for example, see Patent Document 5).
In the above-mentioned Patent Document 5, a user authenticating device registers user authentication information for authenticating the user terminal. Then, the user authenticating device accepts an input of user authentication information from the user terminal, and authenticates the user terminal by using the accepted user authentication information and the registered user authentication information. Therefore, it is possible to provide more flexibility on the authenticating side by using the user terminal held by the user, and authenticate various services.    [Patent Document 1]    Japanese Patent No. 2931276    [Patent Document 2]    Japanese Patent No. 2937820    [Patent Document 3]    Japanese Unexamined Patent Application Publication No. 2001-237950    [Patent Document 4]    Japanese Unexamined Patent Application Publication No. 2001-358827    [Patent Document 5]    Japanese Unexamined Patent Application Publication No. 2003-208409